1. Field of the Invention
The present invention relates to flight maneuverable gas turbine exhaust nozzles and, more specifically, to actuating devices for positioning the flaps of vectoring two-dimensional exhaust nozzles.
2. Description of the Related Art
Two-dimensional jet engine augmented exhaust nozzles capable of providing thrust vectoring for in-flight maneuverability or thrust vectoring for short take-off are designed to meet a multitude of operational capabilities within the flight envelope as illustrated by the positions of the exhaust nozzle flaps depicted in FIGS. 1-3. In FIGS. 1-3, three configurations of exhaust nozzle 100 are illustrated corresponding to straight axial thrust, downward vectored thrust, and upward vectored thrust, respectively. Nozzle 100 includes symmetrically opposed convergent flaps 102 and opposed divergent flaps 104 positioned between sidewalls 106. The opposed convergent flaps, opposed divergent flaps, and opposed sidewalls define an exhaust stream flow path of exhaust nozzle 100 indicated by arrow 120. Relative to a central axis 108 of nozzle 100, the exhaust stream flow path may be directed parallel thereto for pure axial thrust without afterburning, or at an angle to axis 108 for vectored thrust as illustrated in FIGS. 2 and 3. In addition to thrust vectoring it is further desireable to modulate the divergent flaps so as to optimize the exit area of the nozzle as a function of the throat area.
Prior art two-dimensional exhaust nozzles capable of meeting each of the flap configurations illustrated in FIGS. 1, 2, and 3 utilized an independent actuation system to move each of the convergent and divergent flaps. This leads to a large number of actuation systems further leading to increased hydraulic load requirements and a reduction in reliability.
Furthermore, prior art two-dimensional thrust vectoring exhaust nozzles commonly mounted the vectoring actuators for the divergent flaps directly to the convergent flaps. This configuration results in additional reliability problems because hydraulic fluid must be fed to the actuators mounted on the movable convergent flaps through rotating couplings or flexible hoses. Such rotating couplings and flexible hoses commonly exhibit leakage problems thus detracting from the reliability of the system.
Furthermore, independent actuation of each divergent flap may result in fail-safe problems since one of the divergent flaps might open if its actuation system fails causing reduced thrust and unwanted vectoring of the exhaust gas stream.